Doomsday prediction: Will the world end in 2012?

Since the beginning of time, it seems, mankind has been predicting our collective doom.

In ancient and modern times, most apocalyptic predictions are based on religious beliefs that God is ready to call home the faithful and leave the rest of us to sweat it out on a hellish Earth.

We have a new doomsday countdown, and you can thank the ancient Mayans for it. It seems their "Long Count" calendar will reset to zero come Dec. 21, 2012.

Their calendar began in 3114 B.C. and marks time in 394-year periods called "baktuns." The Mayans, known for their advanced mathematics and astrology, held the number 13 in high regard. So, when a tablet was found nearly 50 years ago indicating their God would return in the 13th period, the countdown to our earthly end started.

(The Mayans, by the way, didn't disappear mysteriously from the planet, as some people believe. They gradually assimilated into other cultures after the Spanish colonization and still flourish in parts of South America.)

Doomsday believers, you can hold off on stocking a bomb shelter, for now. Historians scoff at the notion that the Mayan calendar heralds anything sinister.

"For the ancient Maya, it was a huge celebration to make it to the end of a whole cycle," Sandra Noble, executive director of the Foundation for the Advancement of Mesoamerican Studies, told USA Today. To render Dec. 21, 2012, as a doomsday or moment of cosmic shifting, she says, is "a complete fabrication and a chance for a lot of people to cash in."

To that end, we take a look back at other end-of-days predictions that failed to materialize. Whew ... Click on the photo to get started.